Use only one header to send git blobs

app/controllers/projects/avatars_controller.rb

@@ -6,8 +6,7 @@ class Projects::AvatarsController < Projects::ApplicationController
     @blob = repository.blob_at_branch('master', @project.avatar_in_git)
     if @blob
       headers['X-Content-Type-Options'] = 'nosniff'
-      headers['Gitlab-Workhorse-Repo-Path'] = repository.path_to_repo
-      headers['Gitlab-Workhorse-Send-Blob'] = @blob.id
+      headers.store(*Gitlab::Workhorse.send_git_blob(repository, @blob))
       headers['Content-Disposition'] = 'inline'
       render nothing: true, content_type: @blob.content_type
     else

app/controllers/projects/raw_controller.rb

@@ -15,8 +15,7 @@ class Projects::RawController < Projects::ApplicationController
       if @blob.lfs_pointer?
         send_lfs_object
       else
-        headers['Gitlab-Workhorse-Repo-Path'] = @repository.path_to_repo
-        headers['Gitlab-Workhorse-Send-Blob'] = @blob.id
+        headers.store(*Gitlab::Workhorse.send_git_blob(@repository, @blob))
         headers['Content-Disposition'] = 'inline'
         render nothing: true, content_type: get_blob_type
       end

lib/api/repositories.rb

@@ -57,8 +57,7 @@ module API
         not_found! "File" unless blob
 
         content_type 'text/plain'
-        header 'Gitlab-Workhorse-Repo-Path', repo.path_to_repo
-        header 'Gitlab-Workhorse-Send-Blob', blob.id
+        header *Gitlab::Workhorse.send_git_blob(repo, blob)
       end
 
       # Get a raw blob contents by blob sha
@@ -84,8 +83,7 @@ module API
         env['api.format'] = :txt
 
         content_type blob.mime_type
-        header 'Gitlab-Workhorse-Repo-Path', repo.path_to_repo
-        header 'Gitlab-Workhorse-Send-Blob', blob.id
+        header *Gitlab::Workhorse.send_git_blob(repo, blob)
       end
 
       # Get a an archive of the repository

lib/gitlab/workhorse.rb

+require 'base64'
+require 'json'
+
+module Gitlab
+  class Workhorse
+    class << self
+      def send_git_blob(repository, blob)
+        params_hash = {
+          'RepoPath' => repository.path_to_repo,
+          'BlobId' => blob.id,
+        }
+        params = Base64.urlsafe_encode64(JSON.dump(params_hash))
+
+        [
+          'Gitlab-Workhorse-Send-Data',
+          "git-blob:#{params}",
+        ]
+      end
+    end
+  end
+end
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